A main object of the invention is to provide a noveluseful vitamin D3 derivative, which has an excellentvitamin D3 activity and, as compared with conventionalvitamin D3 derivatives, has a relatively small amount ofinfluence on the systemic calcium metabolism. Theinvention includes a 9,10-secopregnane derivative of thefollowing general formula [1] and a pharmaceuticalcomposition containing it as active ingredient.[Formula 1](see Formula 1)In the general formula [1], the following partial structurebetween the 16-position and the 17-position means a singlebond or a double bond:[Formula 2](see Formula 2)Y is a single bond, an alkylene, an alkenylene orphenylene； R1 and R2 are the same or different, eachrepresents hydrogen, an alkyl or a cycloalkyl； or R1 and R2,taken together with the adjacent carbon atom, form acycloalkyl； R3 is hydrogen or methyl； Z is hydrogen,hydroxy or -NR11R12.118
